1. Field of the Invention
The present invention relates to novel addition compounds of dipeptide derivative and amino acid derivative and a process for producing the addition compound. More particularly, it relates to novel addition compounds of the dipeptides composed of N-substituted monoamino dicarboxylic acid ester residues and amino carboxylic acid ester residues, with amino carboxylic acid esters and processes for producing the addition compound utilizing an enzymatic reaction and for decomposing the addition compound.
2. Description of the Prior Art
It has been known that protease such as papain and chymotrypsin are used for forming peptide bonds as the reverse reaction of protein decomposition. For example, anilides have been produced by using papain by Bergman and the peptide syntheses using monoamino monocarboxylic acids such as leucine having an N-terminal protective benzoyl group and leucine and glycine both having a C-terminal protective amide or anilide group have been attained with papain and chymotrypsin by Fruton. (Advances in Protein Chemistry Vol. 5, page 33 (1949). Academic Press Inc. New York, N.Y.)
Recently, some of the inventors reported peptide syntheses using amono acids having an N-terminal protective benzyloxycarbonyl group and amino acids having a C-terminal ester group with enzymes such as papain, Prolisin, subtilisin BPN', etc. (Abstracts of the 35th Autumun Conference of the Chemical Society of Japan, PP482 and 486 (1976).
In these processes, the products are deposited in an aqueous medium as water insoluble products resulted by losing water soluble groups (this is necessary to force the reversible reaction toward the peptide formation). Accordingly, when a water soluble group should still be remained in the reaction product, for example, as in the case wherein the aminoacids having a second carboxyl group at the side chain (e.g., aspartic acid and glutamic acid) are used as the starting compound, it has been assumed to be desirable that the wtater sluble group of the starting compound be masked with a less hydrophilic protective group.
The inventors have studied further on these systems and have found that, when monoaminodicarboxylic acids such as aspartic acid and glutamic acid which has an N-terminal protective group are used as the starting compounds, the resulting dipeptides themsleves are not deposited, however, and that, when specific amino acids having a C-terminal ester group (amino carobxlic acid esters) are chosen for the counter part starting compounds, addition compounds of the dipeptides which are enzymatic reaction products, and the amino acid esters are deposited.
It has been known that peptide derivatives have various physiological activities, and these peptide derivatives can be produced by various methods. The peptides having acidic amino acid residue such as .alpha.-L-aspartylphenylalanine lower alkyl ester useful as a sweetening compound can be obtained from a precursor having a benzyloxycarbonyl group as an N-terminal protective group by removing the protective group.
The peptides having an N-terminal protective group such as N-benzyloxycarbonyl-L-.alpha.-glutamyl phenylalanine lower alkyl ester can be easily hydrolyzed to lead peptides having a bare C-terminal carboxyl group, and these hydrolyzed peptides have been used as substrates for measuring enzymatic activity of a carboxypeptidase.
The N-protected or -unprotected dipeptide esters can be obtained by reacting acidic amino acid anhydride having an amino group protected or unprotected with an amino acid alkyl ester (Japanese Patent Publication No. 14217/1974 and Japanese Unexamined Patent Publication Nos. 61451/1973, 76835/1973, 58025/1975 and 71642/1975).
However, the desired dipeptide esters can not be obtained easily by the conventional processes, since according to these processes, dipeptide esters having peptide bonds at the side chain carboxyl groups of the acidic amino acids are inevitably produced with the desired ones.